The invention relates to a method for operating a device for controlling an electrodynamic brake of an electric camshaft adjuster for an internal combustion engine wherein, in a cascade control, the phase position of the camshaft adjuster is controlled by a position controller and the phase angle is controlled by an adjustment speed controller.
The phase angle of a camshaft with respect to a crankshaft of an internal combustion engine can be changed by passive (driveless) camshaft adjusters. These camshaft adjusters comprise, for example, a brake and a summing gear (DE 100 38 354 A1) or a brake and a lever mechanism (DE 102 47 650 A1), wherein the lever mechanism acts like a summing gear. Generally, hysteresis brakes which are contactless and operate without wear are used as the brakes.
In order to maintain and adjust the phase angle, a controller is necessary since it is the variable torque of the brake at the actuating input of the summing gear, i.e. at the actuating shaft, which brings about changes in the phase angle of the camshaft. Applying the brake slows down the actuating shaft and thus changes the phase angle by means of the summing gear, and, with a negative gear mechanism as the summing gear, the phase angle is adjusted in the advance direction.
If the brake is released, the actuating input accelerates due to the load torque of the camshaft and the phase angle is adjusted in the retarding direction if a negative gear mechanism is used. If the phase angle is to be constant, a coupling situation needs to be established in which there is no relative movement in the gear mechanism, that is, the actuating shaft must be held at the camshaft rotational speed.
A control structure for the adjustment motor of an electric camshaft adjuster according to the prior art is known, for example, from German laid-open application DE 102 51 347 A1. A control structure for reaching the setpoint adjustment rotational speed of an adjustment motor for the electric camshaft adjuster is described in said document, wherein the camshaft adjuster includes at least one controller which generates control signals for the adjustment motor from measurement signals of the internal combustion engine.
The controller has a differential signal composed of setpoint values and actual values as the input signal, and a regulated setpoint adjustment rotational speed, which is intended for the adjustment motor and to which a nonregulated rotational speed signal is added, as the output signal. Different embodiments of a position controller, a rotational speed controller, a combined position and rotational speed controller and a two-point current controller as an example of a current limiting function are proposed.
It is the principal object of the present invention to further improve the control behavior of a control structure or the control structure of a camshaft adjuster of an internal combustion engine.